Screw modifier problem
The object origin should be in the middle, not on the thread. Because the object origin is what the modifier uses as a reference for rotation.

If you look at the first screenshot, you can see how the object's origin is at the center line of the bulb, surrounded by the translation widget. Only the edges are left.

In object mode with only the object selected, set the cursor to the object using SHIFTS "Cursor to Selection". That will make sure the cursor is on the same plane as the object. Then place the cursor on the symmetry line of the bulb and use "Set Origin" >> Origin to 3D Cursor from the tools panel on the left.

You might need to adjust the axis that the modifier uses in its settings.